This invention relates to a speech information processor advantageously employed in an electronic musical instrument or a television game device.
The sound source employed in general in an electronic musical instrument or a television game may be roughly classified into an analog sound source, comprising a voltage-controlled oscillator (VCO), a voltage-controlled amplifier (VCA), a voltage-controlled filter (VCF) etc., and a digital sound source, such as a programmable sound generator (PSG) or a zigzag readout type ROM.
As an example of the digital sound source, the JP Patent Kokai (Laid-Open) Patent Publication No. 62-264099 (1987) or the JP Patent Kokai (Laid-Open) Patent Publication No. 62-267798 (1987) discloses a sampler sound source in which sound source data sampled from the live instrument sound and digitally processed is stored in a memory for use as the sound source.
The above-mentioned sound source (sampler sound source) stores only sound source data of a pre-set pitch (interval) after compression by, for example, non-linear quantization. Each sound source data is stored in two parts, that is in a formant portion (FR) and a one-period portion (LP) of plural repeated waveforms of the fundamental period following the formant portion, as shown in FIG. 9. The formant portion is a signal waveform at the initial stage of sound production proper to each musical instrument, such as a sound produced when a key of a keyboard is struck until a hammer hits the string in the case of a piano. During readout of the sound source data, the formant portion is read out first and the one-period portion is read out a number of times.
Since the above sound source data is compressed, and only the required portions, that is the above formant portion and the one-cycle repetitive portion, are extracted and stored, a large quantity of sound source data may be stored in a smaller storage space.
As a general speech information processor for data processing of the sampler sound source, there is known an audio processing unit (APU) 107 consisting of a digital signal processing unit (DSP) 101, a memory 102 and a central processing unit (CPU) 103, as shown in FIG. 10.
In this figure, the APU 107 is connected to a host computer 104, provided in a typical personal computer, a digital electronic musical instrument or a TV game machine.
The host computer 104 includes a ROM cassette storing the above-mentioned sound source data, control programs, etc. The control program stored in the ROM cassette is read out by the CPU 103 so as to be stored in a working memory 103a therein.
The CPU 103 causes the sound source data to be read out from the ROM cassette and transiently stored in the memory 102 via the DSP 101, based upon the above-mentioned control program by way of performing writing control for the memory 102. The CPU 103 also controls the DSP 101 in accordance with the control program. The DSP 101 causes the sound source data stored in the memory 102 to be read out under control by the CPU 103 and processes the sound source data thus read out with, for example, bit expansion or pitch conversion. The DSP 101 also processes the sound source data with looping for reading out the repetitive portion of the sound source data a number of times. The sound source data, outputted by the DSP 101 after such processing operations, is fed by a D/A converter 105 and thereby converted into analog speech signals which are fed to a speaker unit 106. Thus an acoustic output corresponding to the speech sound data can be produced via the speaker unit 106.
The access time to the memory 102 by the CPU 103 and the DSP 101 is pre-set so that the CPU 101 accesses the memory 102 once after the DSP 101 accesses the memory twice. Consequently, when partially rewriting the sound source data of the memory 102, the CPU 103 controls the writing in the memory 102 so that the CPU reads out sound source data from the ROM cassette and writes the data in the memory 102 during the time the DSP 101 is not accessing the memory. This enables the acoustic output corresponding to the rewritten sound source data to be produced from the next time on. The present Assignee has filed a related patent application under the EP Publication No. 0543667 and a corresponding US patent application (now pending).
However, with the above speech information processor employing the APU 107, the memory 102 is used in common by the DSP 101 and the CPU 103, and the access time of the DSP 101 and the CPU 103 to the memory 102 is pre-set, such that the it is possible for the CPU 103 to have access to the memory only at the pre-set timing. Hence high-speed data transfer cannot be achieved.
Conversely, the high-speed CPU cannot be employed because high speed data transfer cannot be achieved.
If memory access is via an interrupt, for example, for achieving high-speed data transfer, when speech data is being read out by the DSP 101, speech data readout is necessarily interrupted, such that speech data outputting cannot be made continuously.